Fixed the parser to reject SQLSTATE '00000',
since '00000' is the successful completion condition,
and can not be caught by an exception handler in SQL.


mysql-test/r/sp-error.result:
  Bug#8759 (Stored Procedures: SQLSTATE '00000' should be illegal)
mysql-test/t/sp-error.test:
  Bug#8759 (Stored Procedures: SQLSTATE '00000' should be illegal)
sql/sp_pcontext.cc:
  Bug#8759 (Stored Procedures: SQLSTATE '00000' should be illegal)